An amplifier is designed to provide gain to an input signal to generate an amplified output signal. In integrated circuits, one common amplifier design employs transistors coupled in a cascode configuration. A cascode amplifier provides gain to the input signal usually over a specific linear operating range. If the magnitude of the input signal falls outside the linear operating range, then undesirable non-linear components such as third-order inter-modulation distortion (IMD3) components may arise in the amplifier output.
One way to reduce the level of IMD3 in the cascode amplifier output is to provide an auxiliary signal path coupled in parallel with the principal cascode signal path. The auxiliary path may be designed to generate an auxiliary current to cancel the IMD3 components in the output current when combined with the principal cascode current. See, e.g., Kim, Namsoo, et al., “A Cellular-Band CDMA 0.25-um CMOS LNA Linearized Using Active Post-Distortion,” IEEE Journal of Solid-State Circuits, Vol. 41, No. 7, July 2006.
One limitation of techniques utilizing such an auxiliary path is that the signal gain of the cascode amplifier may be significantly reduced along with the IMD3 components. It would be desirable to provide techniques to reduce the IMD3 components in the output signal of a cascode amplifier without significantly reducing the amplifier signal gain.